DE3513208A1 - MAGNETIC RECORDING MEDIUM CONTAINING A SPECIAL COPOLYMER BINDING AGENT - Google Patents

Description

The invention relates to magnetic recording media such as magnetic tapes, fioppy disks, hard disks and the like and particularly magnetic recording media, soft are particularly suitable for use with magnetic disk devices such as computers.

Magnetic recording media used in recording and Information playback devices such as magnetic disk devices are of the type used is prepared by preparing a magnetic coating composition in a solvent containing the appropriate resin binder (Synthetic resin binder) dissolved / dispersed magnetic powder is applied to a non-magnetic substrate or a non-magnetic carrier and baked and the applied coating compound is cured.

Since recording and reproducing devices for information have ever higher performance, there is an er ^

increased demand for magnetic recording media with high ί

rer density. To meet this need, a number of *

of magnetic recording media which include, for example, a medium whose magnetic recording layer has a smaller thickness than is used for normal applications, a medium, which has a magnetic recording layer composed of a completely uniform dispersion of magnetic powder and magnetic recording media using magnetic powder having high coercive force e.g. magnetic, Co-modified gamma-Fe ~ O, powder, magnetic C ^ O ^ powder and magnetic metal powder .

When the magnetic recording layer is made thin, the amount of magnet powder is also decreased. It is essential not to reduce the amount of magnetic powder,

but rather to reduce the amount of the other ingredients such as a binder. However, if the amount of one When the binder is decreased, properties of the magnetic recording medium such as durability are necessarily reduced or service life.

On the other hand, magnetic powders with high coercive force are common available in the form of small size particles and they have a high "needle ratio" (length to width ratio), so that they have a large specific surface. This is disadvantageous because of such powders does not disperse as easily as conventional gamma Fe ^ O -, - powder. It takes a longer time before the magnetic powders are dispersed in order to form uniform magnetic coatings to obtain. The lengthy dispersion process results in a lowering of the coercive force as a result of the Breakage of the magnetic powder.

It is an object of the present invention to provide a magnetic recording medium in which any Magnetic powder works very well in a magnetic coating mass without performing kneading for dispersed for longer periods of time, the magnetic recording layer having good mechanical strength, even if only a very thin layer is made and with the good magnetic properties as a result of the excellent Dispersion of the magnetic powder can be ensured.

Surprisingly, it has now been found that when using of a specific type of copolymer resin as part of a binder for the dispersion of magnetic powders is essential better magnetic recording media can be obtained can.

A magnetic one is therefore used to solve the aforementioned problem A recording medium which is characterized in that it is used as a binder for a magnetic recording layer a copolymer of maleic anhydride and an olefinically unsaturated monomer, which with maleic anhydride

preferably

hydride is copolymerizable, / in combination with a thermosetting resin _/ is used. The copolymer gives good dispersion of any type of magnetic powder in a resin binder.

The invention is explained in more detail below with reference to embodiments.

The copolymers useful in practicing the invention are made from maleic anhydride and olefinically unsaturated ones Monomers prepared by any method. The olefinic unsaturated monomers include alkenes having 2 to 18 carbon atoms and preferably 2 to 8 carbon atoms, e.g., ethylene, propylene, butene, pentene, hexene, heptene, octene, and the like; Alkyl esters of acrylic acid and / or methacrylic acid, in which the alkyl radical has 1 to 18 and preferably 1 to 8 carbon atoms, e.g. the methyl, ethyl, Propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, Decyl radical and the like; Vinyl chloride and styrene. These olefinically unsaturated monomers can be used individually or in combination can be used, e.g. acrylates can either be used individually or in combination or with methacrylates, Alkenes, styrene and / or vinyl chloride can be used.

In view of compatibility with other resins, the copolymers generally have a molecular weight from about 500 to 50,000, preferably from about 1,000 to 10,000. The content of maleic anhydride in the copolymers is in the range from about 5 to 80 mol%, preferably from 20 to 50 mol%. Within these areas is the dispersibility of magnet powder in a synthetic resin binder containing the copolymer is significantly improved.

In terms of the surface properties of a magnetic Recording medium in which a binder of the foregoing Copolymers were used, the copolymers should be used in combination with thermosetting resins, as they are usually used for these purposes are used. The resins used in combination are thermosetting resins, which have functional groups which lead to a condensation reaction with the reactive groups of the maleic anhydride units in the copolymer are capable. The functional groups can be glycidyl groups in epoxy resins, methylol and / or Hydroxyl groups in phenolic resins, urea resins, polybutyral resins and the like. Specific and preferred examples of the thermosetting resins include epoxy resins, phenol resins, Melamine resins, urea resins, acrylic resins, butyral resins, and mixtures thereof. The copolymer is preferred in combination with epoxy resins and particularly preferably with mixtures of epoxy resins and phenolic resins, epoxy resins and melamine resins, Epoxy resins and acrylic resins as well as epoxy resins, phenolic resins and acrylic resins or polyvinyl butyral are used. Such Mixtures should consist predominantly of epoxy resins. In practice, the copolymer is used in an amount of from about 1 to 50% by weight and preferably 5 to 20% by weight, based on the total binder, are used.

The binder containing the maleic anhydride copolymer is used in an amount of 30 to 200 parts by weight, preferably from 50 to 120 parts by weight, used per 100 parts by weight of magnetic powder.

The magnetic powders used in the present invention can be any magnetic metal powders commonly used in the art, and they include, for example, ferromagnetic iron oxides such as gamma-Fe2O3 and ϊ ^ Ο ^ with or without addition of Co, Ni, Mn and the like. ferromagnetic metals such as Co, Ni, Fe and alloys thereof such as Fe-Co, Fe-Ni, Co-Ni, Fe-Co-Ni, and other ferromagnetic materials such as CrO ₂ , barium ferrite, and the like.

Although these magnet powders have a very small grain size, they easily become in the binder resin containing the copolymer maleic anhydride based dispersed. The size of the powders is generally in the range of 0.05 to 2 um.

For the manufacture of a magnetic recording medium is a magnetic powder in a synthetic resin binder which contains the above-described copolymer, and a solvent for the binder using a suitable mixer or kneading device. The magnetic coating obtained is applied to a non-magnetic support on at least one side piled therefrom, and it is dried and baked under the condition of a temperature of 50 to 250 ° C for sufficient time for curing and / or for the condensation reaction between the copolymer to occur and a thermosetting resin. The coating can be made by any known technique, e.g. by spin coating, air knife coating, knife coating, Dip coating, multiple roller coating, spray coating and the like. By using the copolymer, the dry strength of the recording layer can even be reduced to 0.5 µm, although it is generally in the range of 1 to 10 µm.

Non-magnetic supports can be disks, films, foils or plates made of a variety of materials, these being e.g. synthetic and semi-synthetic resins such as polyesters, polyolefins, cellulose derivatives and the like, metals such as aluminum, magnesium, copper and the like, glasses and ceramic materials.

In addition to the magnetic powders, various additives can be added to the magnetic coating material. Such Additives include lubricants, dispersants, stabilizers, plasticizers and the like.

The use of the copolymers of maleic anhydride and olefinically unsaturated monomers has a number of advantages, namely:

(1) The dispersibility of magnetic powder becomes significant is improved, and the breakage of the magnetic powder during the dispersion process is improved Avoided to the extent that lowering of the coercive force and the square ratio of the magnetic obtained Recording medium are avoided;

(2) the grinding or kneading time for the magnetic dope can be reduced to a great extent so that the time becomes about half that for conventional magnetic Coating compositions required time with equivalent surface properties of the magnetic recording medium reduced. This leads to a great reduction in manufacturing time and cost;

(3) It becomes not only high mechanical strength but also good adhesion, abrasion resistance and solvent resistance a magnetic recording layer achieved because the crosslinking of the thermosetting resins with the Copolymers, as previously explained, takes place. In the case of magnetic disks, the wear resistance is enhanced by the Number of contact start-stop (CSS) cycles determined, and the one prescribed in ISO standard TC97 / SC1ON228 The limit value is above 10,000. A magnetic disk produced according to the invention has a value that is very high is higher than this limit. The waste of magnetic powder is eliminated in a magnetic recording medium of the present invention hardly found. In addition, the magnetic recording layer is made up of the copolymer Maleic anhydride base contains, very resistant to solvents such as alcohols, whereby such alcohols for washing magnetic disks on their surfaces

are applied, so that the magnetic disks according to the invention are very durable.

The invention is explained in more detail by means of the following examples, where the data in parts relate to weight.

example 1

100 tIe. Magnetic powder made from Co-deposited gamma-Fe ₂ Ow 10 Tie. alpha-Al ₀ O powder, 45 teas. a commercially available epoxy resin (Epikote 1007 from Shell Petrochem. Inc.), 20 TIe. a commercially available phenolic resin (Sumirac PC-25, Sumitomo Bakelite Co., Ltd.), 10 Tie. an alternating copolymer of butyl acrylate / maleic anhydride with a molar value of butyl acrylate / maleic anhydride of 50/50 and a weight average molecular weight of about 5000 and 620 parts. a mixed solvent of toluene and ethylene glycol monobutyl ether were placed in a ball mill and kneaded for 24 hours to prepare a magnetic dope.

The magnetic coating material was applied to an aluminum alloy carrier, followed by baking and hardened at 200 ° C for 1 hour and polished in the usual way for the production of a magnetic disk.

Example 2

The general procedure of Example 1 was repeated using a kneading time (meal) of 12 hours and a magnetic disk was made.

Example 3

100 tIe. Magnetic powder from Co-deposited GaITUTIa-Fe ₂ O ₃ , 10 TIe. alpha-Al ₂ O «powder, 35 teas. a commercially available epoxy resin (Epikote 1001 from Shell Petrochem. Inc.), 25 TIe.

a commercially available acrylic resin (Dyanal SE-5437 by Mitsubishi Rayon Co., Ltd.), 15 Tie. of a random copolymer Ethyl acrylate / maleic anhydride, in which the maleic acid

anhydride molecules are not directly bound to one another and in which the molar value of ethyl acrylate / maleic anhydride was 60/40 and that was a weight average molecular weight owned by about 2000, as well as 620 TIe. a mixed solvent of toluene and ethylene glycol monobutyl ether were used to prepare a magnetic coating material and further a magnetic disk in the same manner as used in example 1.

Comparative example

1Q0 TIe. Co-deposited gamma Fe ₃ O ₃ , 10 Tie. alpha-A ^ O.,, 50 Tie. Commercial epoxy resin (Epikote 1007), 25 Tie. Phenolic resin (Sumirac PC-25) and 620 TIe. a mixed solvent of toluene and ethylene glycol monobutyl ether were used to prepare a magnetic coating material and a magnetic disk according to the procedure of Example 1.

Those prepared in Examples 1 to 3 and in the comparative example Magnetic disks were measured for their magnetic properties, i.e., coercive force and Square ratio, surface defects and abrasion resistance. The results are compiled in Table 1 below.

Table 1

Coercive force square surface abrasion

(Oe) ratio of defective resistance (CSS cycles)

E.g. 1 680 0.86 0 > 30000 Il 2 685 0.88 2 > 30000 Il 3 690 0.89 0 > 30000 Cf. • E.g. 660 0.80 8th 18000

From the results of the table it can be seen that the invention Magnetic disks have better magnetic properties than

the Vergieichspiatte. This is the good dispersibility of the magnetic powder due to the presence of the copolymer attributed, whereby the magnet powder is less broken at the time of the grinding treatment or kneading treatment.

The number of surface defects is also greatly reduced and the abrasion resistance is so great that the medium can be used semi-permanently.

If, in addition, the meal or kneading time is reduced to half the time conventionally required, the plate obtained in this way is still excellent, as can be seen from the results of Example 2.

Example 4

The general procedure of Example 1 was repeated using an alternating copolymers of butyl methacrylate / Maleic anhydride was used, which has a molar value of butyl methacrylate / maleic anhydride of 50/50 and a weight average molecular weight of about 5,000, and a magnetic disk was made again.

Example 5

The general procedure of Example 4 was repeated except that the kneading time (meal) was in the ball mill was reduced to half, i.e., 12 hours, and a magnetic disk was made again.

Example 6

The general procedure of Example 3 was repeated using a random copolymer of methyl methacrylate / Maleic anhydride, which has a methyl methacrylate / maleic anhydride molar value of 60/40 and a weight average molecular weight from about 2000 was used and a magnetic disk was made herewith.

3S13208

Examples 7 to 9

The general procedure of Example 1 was repeated using an alternating copolymer of pentene / maleic anhydride having a pentene / maleic anhydride molar value of 50/50 and a weight average molecular weight of about 5000 in Example 7, an alternating copolymer of vinyl chloride / maleic anhydride with a molar value of vinyl chloride / maleic anhydride of 50/50 and a weight average molecular weight of about 5000 in Example 8 and a alternating copolymer of styrene / maleic anhydride with a styrene / maleic anhydride molar value of 50/50 and one Weight average molecular weights of about 5,000 were used in Example 9, and magnetic disks were made manufactured.

Examples 10 to 12

The general procedure of Examples 7-9 was repeated except that the ball mill treatment time was reduced to half, i.e., 12 hours, and magnetic disks were made again.

Examples 13-15

The general procedure of Example 3 was repeated using a random copolymer of ethylene / maleic anhydride having an ethylene / maleic anhydride molar value of 60/40 and a weight average molecular weight of about 2000 for Example 13, a vinyl chloride / maleic anhydride random copolymer having a vinyl chloride / maleic anhydride molar value of 60/40 and a weight average molecular weight of about 2000 for Example 14 and a styrene / maleic anhydride random copolymer having a styrene / maleic anhydride molar value of 60/40 and a weight average molecular weight of about 2000 was used for Example 15, and magnetic disks were made.

The magnetic disks obtained in Examples 4 to 15 became subjected to measurements in the same manner as in Examples 1 to 3; the results are compiled in Table 2 below :

Table 2

4th Coercive force
(Oe) square
relationship Surfaces-
defective Abrasion resistance
age
(Ces cycles) E.g. 5 680 0.86 0 > 30000 Il 6th 685 0.87 3 > 30000 Il 7th 690 0.89 0 > 30000 Il 8th 680 0.86 0 > 30000 Il 9 675 0.87 0 > 30000 Il 10 680 0.86 0 > 30000 Il 11th 690 0.88 1 > 30000 Il 12th 680 0.88 2 > 30000 Il 13th 685 0.86 3 > 30000 Il 14th 685 0.87 1 > 30000 Il 15th 680 0.87 1 > 30000 Il .E.g. 685 0.87 1 > 30000 Cf. 660 0.80 8th 18000

When alkyl methacrylates, alkenes, vinyl chloride and styrene are used as
olefinically unsaturated monomer are used
results are similar to those in Examples 1 to 3.

Claims (7)

EUROPEAN PATENT ATTORNEYS MANITZ, Fl NSTERWALD & ROTERM UN D35 1 320B VICTOR COMPANY OF JAPAN, LTD. No. 3-12, Moriya-cho, Kanagawa-ku Yokohama, Japan GERMAN PATENT LAWYERS DR. GERHART MANITZ · dipl.-phys. MANFRED FINSTERWALD dipl.-ing., Dipl.-economics-ing. HANNS-JÖRG ROTERMUND ■ Dipl.-Phys. DR. HELIANE HEYN · dipl-chem. WERNER GRÄMKOW DIPL-ING. (1939-1982) BRITISH CHARTERED PATENT AGENT JAMES G. MORGAN B.SC. (PHYS), D.M.S. GRANT REPRESENTATIVE AT THE EUROPEAN PATENT OFFICE REPRESENTATIVES BEFORE THE EUROPEAN PATENT OFFICE MANDATAIRES AGREES PRES L1OFFICE EUROPEEN DES BREVETS 8000 MUNICH 22 ROBERT-KOCH-STRASSE TELEFON (0 89) 224211 + III) TELEGRAMS INDUSTRIAL PATENT MUNICH Munich, P / Sv-V 2283 April 12th, 1985 Magnetic recording medium with a content of a special copolymer binder. Patent claims 1. A magnetic recording medium comprising a non-magnetic substrate and one formed on the substrate, magnetic recording layer, which is made of a composition which is one in one The resin binder comprises dispersed magnetic powder characterized in that the resin binder contains a copolymer of maleic anhydride and an olefinically unsaturated monomer. MANlTZ FiNSTERWALD ■ HEYfJ MORGAN 8000 MUNICH 22 ROBERT-KOCH-STRASSE 1 · TEL. (0 89) 22 4211 ■ TELEX 5? 9 672 PATMf FAX lO89i ? ') ' 5 Γ5 HANNS-JCRG ROTERMUND ■ 7000 STUTTGART 50 (BAD CANNSTATT) ■ SEELBERGSTR. 23/25 TEL. IßT 11) 56 72 BI BAYER VOLKSBANKEN AG MUNICH BLZ 70090000 ACCOUNT 7270 POST CHECK: MUNICH 77062-805 3AYEP. VEREiNSBANK ■ MUNICH ■ BLZ 700 202 70 · ACCOUNT 578 351 · BAYER. HYPO- AND EXCHANGE BANK · MUNICH · BLZ 700 200 01 ■ ACCOUNT 6 88C Ί9 930 - 2 - 2. A magnetic recording medium according to claim 1, characterized characterized in that the olefinically unsaturated monomer from alkyl esters of acrylic acid and methacrylic acid, Alkenes, vinyl chloride, styrene or mixtures thereof. 3. Magnetic recording medium according to claim 1, characterized characterized in that the copolymer has a Maieinsäureanhydridgehait has from 5 to 80 mol%. 4. Magnetic recording medium according to claim 3, characterized characterized in that the content is 20 to 50 mol%. 5. Magnetic recording medium according to claim 1, characterized in that the resin binder 1 to 50% by weight of the copolymer and the remainder a thermosetting resin. 6. A magnetic recording medium according to claim 5, characterized in that the thermosetting resin is an epoxy resin or its mixture with another thermosetting resin. 7. A magnetic recording medium according to claim 1, characterized characterized in that the copolymer has a molecular weight of 500 to 50,000, so that a good Compatibility with a thermosetting resin is given.